1. Field of the Invention
This disclosure relates generally to calibration of plenoptic imaging systems.
2. Description of Related Art
The plenoptic imaging system has recently received increased attention. It can be used to recalculate a different focus point or point of view of an object, based on digital processing of the captured plenoptic image. The plenoptic imaging system also finds application in estimating depth to three-dimensional objects that are imaged by the plenoptic imaging system, possibly followed by three-dimensional reconstruction of those objects or the entire three-dimensional scene. Another application is multi-modal imaging, using a multi-modal filter array in the pupil plane of the primary imaging module. Each filter is imaged at the sensor, effectively producing a multiplexed image of the object for each imaging modality of the filter array. Other applications for plenoptic imaging systems include varying depth of field imaging and high dynamic range imaging.
However, the architecture of a plenoptic imaging system is different from that of a conventional imaging system, and therefore requires different calibration and processing procedures. Many plenoptic imaging systems use an array of microlenses. The image captured by the plenoptic imaging system can be processed to create multiple images of the object taken from different viewpoints. These multi-view images carry a level of parallax between them, which corresponds to the three-dimensional structure of the imaged object. This parallax is usually quantified by disparity, which can be defined as an amount of shift that a pixel corresponding to a point in space undergoes from one view to another. The disparity depends on the depth location of the object. In order to convert disparity to an actual depth, a mapping between depth and disparity is required. These mappings typically have been created using a thin lens model for the primary lens in the plenoptic imaging system and a pinhole model for the microlens array. However, for many real plenoptic imaging systems, these assumptions are not particularly good. This is especially true for systems with large optical aberrations, such as field curvature. In such cases, the mapping can vary significantly from the simple thin lens—pinhole model and is highly dependent on the optical characteristics of the system.
Thus, there is a need for better approaches to determine the mapping between depth and disparity for plenoptic imaging systems.